There is a need for improved polymer compositions which are suitable for applying to the surface of various objects, either as a coating which will adhere to the surface, a sealant, adhesive or a coating which can be removed to provide a mold that has the shape and the contours of the surface to which the composition was applied. Commercially speaking, polymer compositions used for these purposes have often been two-part liquid compositions which cure to elastomers or plastics at room temperature. They must be non-sag if they are to be applied to a vertical, overhead or even a horizontal surface without excessive runoff. Such compositions have been generally made by a manufacturer at one location and sold in pails or cans to the user who then mixes the two components at another location.
The individual parts of prior art non-sag two-part compositions have been made non-sag prior to mixing by the user so the user mixes pastes or prethickened liquids. Otherwise, the user mixes the two-part liquid compositions and then must add a third part to thicken the mixture to a suitable non-sag state.
Mixing such pastes or prethickened liquids is difficult and can result in poorly mixed compositions. Also, adding a third component is difficult as well. Compositions which are made non-sag by the manufacturer require extra ingredients which often add nothing to the performance of the compositions to achieve the thickening. Additionally, package stability of such compositions is sometimes a problem.
It is desired in such polymer compositions that coatings formed therefrom are tough with high tear and tensile strengths.
It would be desirable to provide a method of chemical thickening which takes place right after two newtonian liquid parts are mixed which provides the proper degree of non-sag character to the composition and aids curing to a tough polymer at room temperature.
Such two-part compositions would be useful for use as brush-on mold compositions which cure to a flexible rubber mold for casting objects from gypsum plasters, waxes, portland cements and various thermosetting resins such as epoxy resins, polyesters, polyurethane and others. They would be also useful to fill a gap between two surfaces and as coatings which require some non-sag character to achieve proper film build when applied.
Two-part compositions are often preferred for such uses over one-part compositions because they generally contain minimum volatile content, which take time to dry and cause subsequent shrinkage and they may be applied and cured rapidly at room temperature without the use of heat.